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Radiation Therapy > Part VI > Flashcards

Part VI Flashcards

1
Q

Treatment in which the source of the therapeutic agent is at a distance from body

A

Teletherapy

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2
Q

Means distant

A

Tele

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3
Q

Means therapeia

A

Treatment

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4
Q

Major drawbacks of Co 60

A

• High risk of radiation hazard due to radon gas leak produced as a by-product
• High cost of radium
• Large absorption
• Low exposure rate constant
• Low output

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5
Q

invented the cobalt 60 unit in the 1950s

A

Dr. Harold E. Johns

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6
Q

Main Reasons for its Suitability for Teletherapy

A
  1. Availability
  2. High specific activity
  3. Sources that minimize the beam penumbra
  4. Relatively long half-life (5.27 years)
  5. Almost monochromatic high energy photon
    emission (photons of 1.173 MeV and 1.333 MeV in equal quantity).
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7
Q

Fixed head
SSD technique

A

Picker machine

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8
Q

CO 60 source of about 2000 Ci
Two specifically designed rooms were built to adjacent to each other

A

1970
Janus CO 60 machine

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9
Q

Isocentric
SSD 60 cm
Output low
Time taken more

A

Iso-centric CO 60 Therapy machine

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10
Q

Indigenous CO 60 teletherapy machine has a capacity of 200 RMM source and its source to iso-centric distance is 80 cm.
User friendly
Improved radiation safety

A

Bhabhatron

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11
Q

Main components of teletherapy machine

A
  1. Radioactive source
  2. Source housing including beam collimator and source movement mechanism
  3. Gantry and stand in isocentric machines
    4.patient support assembly
  4. Machine console
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12
Q

Co 60 source structure

A

Cylindrical double welded stainless steel
1.0 -2.0 cm diameter
Discs/pellets
Circular end facing pt

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13
Q

C0 60 is produced by irradiating ordinary, stable [..] with [..] in the nuclear reactor

A

59 Co
Neutrons

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14
Q

The decay half life is [..] and the average photon energy is [..]

A

5.26 years
1.25 MeV

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15
Q

REQUIREMENTS FOR A RADIOACTIVE NUCLIDE TOBE A USEFUL TELETHERAPY SOURCE

A
  1. It must emit high gamma rays
  2. Must have a high specific activity
  3. Must have a long half-life
  4. The source must be sealed
  5. Dual encapsulation
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16
Q

Housing for the source

A

Source housing

17
Q

Consists of a steel shell filled with lead for shielding purposes and device for bringing the source in front of an opening in the head from which the useful beam emerges

A

Source Housing

18
Q

Off position, [..] is allowed to flow into the space just below the source
On position [..] pumped out to reservoir

A

Mercury shutter

19
Q

The source is fixed in front of the aperture and the beam can be turned on and off by a shutter so sitting metal jaws

A

Moving jaw

20
Q

Provide beams of desired shape and size rotational movement is continuous and it can your rotate 360°

A

Collimator

21
Q

Can rotate 360°, movement is motorized and controlled into directions continuously

A

Gantry

22
Q

Treatment bed motorized movements

A

Horizontal
Vertical
Lateral

23
Q

Table top (rotation)
Base [rotation]

A

90 Degrees rotation to each side
110° rotation to each side

24
Q

x-rays that Constitute the useful treatment beam

A

Y X-rays

25
Q

Absorbed in the cobalt metal and stainless steel capsules resulting in the emission of breamsstrahlung and small amount of characteristic x-rays

A

B particles

26
Q

Advantages of cobalt 60

A
  1. Simplicity of design and ease of operation
  2. Constancy of beam intensity
  3. Allows predictability of decay with a well-defined half-life
  4. It doesn’t have the day-to-day fluctuations typically found in electrical machines
  5. Cheaper and easy to maintain
27
Q

Disadvantages of cobalt 60

A
  1. Due to its large source, the penumbra is larger than the beam
  2. The need for source replacement after 2 half-lives (approx.)
  3. Poor beam flatness for large fields
  4. emits radiation constantly, thus, the source must be
    shielded when the machine is in the beam-off position to protect the personnel

Radiation Therapy (10 decks)

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